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  • 1
    Electronic Resource
    Electronic Resource
    Soil Anaerobiosis, Microorganisms, and Root Function (1980)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Phytopathology 18 (1980), S. 37-66 
    Details
    ISSN: 0066-4286
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.py.18.090180.000345
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  • 2
    Electronic Resource
    Electronic Resource
    Sensing soil oxygen (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 13 (1990), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Under natural conditions where gaseous exchange between soil and atmosphere is restricted by excess water, the concentration of O2 in the rooting zone can become very low while reduced ions and organic compounds that are potentially phytoxic may accumulate. Mechanisms by which shoots and roots detect, and adjust to, this O2-deficient environment are reviewed. Injury to roots and their inability to function because of insufficient O2 is communicated to the shoot in a variety of ways, so that it adjusts physiologically. Roots may acclimate metabolically to a gradual fall in O2 supply, so that they either improve their tolerance of anoxia, or partially avoid O2-deficiency by structural changes that aid internal transfer of O2 to the roots from the shoot. Molecular mechanisms regulating such metabolic changes, including environmental cues, are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1990.tb01083.x
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  • 3
    Electronic Resource
    Electronic Resource
    The Effect of Histones and Other Basic Macromolecules on Cell Permeability and Elongation of Barley Roots (1970)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 23 (1970), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Low exogenous concentrations of calf-thymus histone, poly-l-lysine and lysozyme inhibit root elongation. These basic macromolecules (polycations) also affect cell permeability resulting in a leakage of ultraviolet light (UV)-absorbing materials and chloride ion from cells. Adenosine 5′-monophosphate was identified as one of the UV-absorbing compounds in the root exudate, by thin layer chromatography. These deleterious effects of polycations on root growth and permeability are reduced in the presence of calcium and other divalent cations. Calcium ion-histone interaction appears to exhibit competitive kinetics and suggests that both calcium and histone compete for attachment to negative sites on cell membrances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1970.tb06446.x
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  • 4
    Electronic Resource
    Electronic Resource
    The influence of oxygen deficiency on ethylene synthesis, 1-aminocyclopropane-1-carboxylic acid levels and aerenchyma formation in roots of Zea mays (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 72 (1988), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The relationship between ethylene production, 1-aminocyclopropane-l-carboxylic acid (ACC) concentration and aerenchyma formation (ethylene-promoted cavitation of the cortex) was studied using nodal roots of maize (Zea mays L. cv. LG11) subjected to various O2 treatments. Ethylene evolution was 7–8 fold faster in roots grown at 3 kPa O2 than in those from aerated solution (21 kPa O2), and transferring roots from aerated solution to 3 kPa O2 enhanced ethylene synthesis within less than 2 h. Ethylene production and ACC accumulation were closely correlated in different zones of hypoxic roots, regardless of whether O2 was furnished to the roots through aerenchyma or external solution. Both ethylene production and ACC concentrations (fresh weight basis) were more than 10-fold greater in the distal 0–10 mm than in the fully expanded zone of roots at 3 kPa O2. Aerenchyma formation occurred in the apical 20 mm of these roots.Roots transferred from air to anoxia accumulated less than 0. 1 nmol ACC (mg protein)-1 for the first 1.75 h; no ethylene was produced in this time. The subsequent rise in ACC levels shows that ACC can reach high concentrations even in the absence of O2, presumably due to a de-repression of ACC synthase. The hypothesis was therefore tested that anoxia in the apical region of the root caused enhanced synthesis of ACC, which was transported to more mature regions (10–20 mm behind the apex), where ethylene could be produced and aerenchyma formation stimulated. Surprisingly, exposure of intact root tips to anoxia inhibited aerenchyma formation in the mature root axis. High osmotic pressures around the growing region or excision of apices had the same effect, demonstrating that a growing apex is required for high rates of aerenchyma formation in the adjacent tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1988.tb06616.x
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of applying etnylene to the root system of Zea mays on growth and nutrient concentration in relation to flooding tolerance (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 52 (1981), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Previous studies have shown increases in the concentration of ethylene in the soil and roots of plants when the soil is water saturated (flooded). In Zea mays L. this occurs in association with an overall reduction in growth but without extensive foliar senescence and in conjunction with the development of an adventitious root system. We have assessed the possibility that ethylene may be involved in these responses to flooding. Mixtures of the gas in air were therefore supplied to the roots and stem-base of Z. mays growing in nutrient solution.Seven or 14 d exposure to ethylene (1 or 5 νl 1−1) inhibited seminal root elongation and growth in dry weight and accelerated the emergence of adventitious roots, although their final length and dry weight were depressed. Leaf extension was inhibited by 0.1,1.0 or 5.0 μl 1−1 ethylene around the roots; leaves extending rapidiy at the start of treatment were the most sensitive. Final shoot fresh and dry weights were depressed by the gas but tie shootrroot dry weighl ratio and percentage dry matter were not affected greatly. Leaf chlorosis was not observed but the concentration of phosphorus in the shoots was 26 to 31% below normal.When aeration of the nutrient solution was stopped, the concentration of dissolved oxygen declined and the concentration of ethylene in the roots increased. Similar changes occur in response to soil flooding. Root and shoot growth was slowed by non-aeration although the shootroot dry weight ratio remained unchanged. The phosphorus concentration of the shoots was depressed but there was little chlorosis or leaf death. The similarity in these respects between the effects of ethylene and non-aeration suggests that in flooded Z. mays, ethylene contributes to their development by accelerating the emergence of adventitioos roots, inhibiting phosphorus accumulation in the shoots and by a non-toxic inhibition of plant growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1981.tb06028.x
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  • 6
    Electronic Resource
    Electronic Resource
    Electron microscopy of gas space (aerenchyma) formation in adventitious roots of Zea mays L. subjected to oxygen shortage (1983)
    Springer
    Planta 157 (1983), S. 350-357 
    Details
    ISSN: 1432-2048
    Keywords: Aerenchyma ; Gas space (roots) ; Oxygen shortage (roots) ; Zea (aerenchyma)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper examines the ultrastructure of cortical cells in maize root tips during the early stages in lysigenous aerenchyma formation, promoted by oxygen-deficient nutrient solution. The aim was to determine whether changes in fine structure were compatible with oxygen starvation as the primary cause of cell degeneration and death. There was an initial collapse of some cortical cells, indicating loss of turgor, and the cytoplasm became more electron dense. Mitochondria and endoplasmic reticulum appeared normal at this early stage though the tonoplast lost its integrity. Subsequently the cytoplasm became less electron dense than surrounding healthy cells, and underwent further degeneration while the plasmalemma retracted from the cell wall. Cell walls remained unaltered until this stage, but some then became thin and electron transparent. No cells of the stele were found to degenerate. These observations, which do not readily accord with the hypothesis that oxygen starvation was the cause of cell death, are compared with detailed studies of cell degeration in other cell types. An alternative mechanism for the stimulation of cortical cell lysis in poorly oxygenated roots involving the hormone ethylene, is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397407
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  • 7
    Electronic Resource
    Electronic Resource
    Changes in the kinetics of phosphate and potassium absorption in nutrient-deficient barley roots measured by a solution-depletion technique (1984)
    Springer
    Planta 160 (1984), S. 490-499 
    Details
    ISSN: 1432-2048
    Keywords: Hordeum (ion uptake) ; Ion uptake ; Nutrient deficiency ; Phosphate uptake (root) ; Potassium uptake (root)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract From measurements of the rates of depletion of labelled ions from solution in the low concentration range, we described the phosphate and potassium uptake characteristics of the roots of intact barley plants in terms of the kinetic parameters, K m and I max (the maximum rate of uptake). In relatively young (13 d) and older (42 d) plants, cessation of phosphate supply for 4 d or more caused a marked increase in I max (up to four times), without concomitant change in K m, which remained between 5 and 7 μM. By contrast, 1 d of potassium starvation with 14-d plants caused a decline in the K m (i.e. an increased apparent affinity for potassium) from 53 μM to 11 μM, without alteration to I max. After longer periods of potassium starvation, I max increased (about two times) while the K m remained at the same low value. Growth of shoots and roots were unaffected by these treatments, so that concentrations of ions in the tissues declined after 1 d or more of nutrient starvation, but we could not identify a characteristic endogenous concentration for either nutrient at which changes in kinetic parameters were invariably induced. The possible mechanisms regulating carriermediated transport, and the importance of changes induced in kinetic parameters in ion uptake from solution and soil are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00411136
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  • 8
    Electronic Resource
    Electronic Resource
    Uptake and long-distance transport of phosphate, potassium and chloride in relation to internal ion concentrations in barley: evidence of non-allosteric regulation (1984)
    Springer
    Planta 160 (1984), S. 500-507 
    Details
    ISSN: 1432-2048
    Keywords: Chloride uptake (root) ; Hordeum (ion uptake) ; Ion uptake ; Nutrient deficiency ; Phosphate uptake (root) ; Potassium uptake (root)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The extent to which uptake and transport of either phosphate, potassium or chloride are controlled by the concentration of these ions within the root, perhaps through an allosteric mechanism, was investigated with young barley plants in nutrient solution culture. Plants were grown with their roots divided between two containers, such that a single seminal root was continuously supplied with all the required nutrient ions, while the remaining four or five seminal roots were either supplied with the same solution (controls) or, temporarily, a solution lacking a particular nutrient ion (nutrient-deficient treatment). Compared with controls, there was a marked stimulation of uptake and transport of labelled ions by the single root following 24 h or more of nutrient dificiency to the remainder of the root system. This stimulation, which comprised an increased transport to the shoot and, for all ions except Cl-, increased transport to the remainder of the root system, took place without appreciable change in the concentration of particular ions within the single root. However, nutrient deficiency quickly caused a lower concentration of ions in the shoot and the remaining roots. The results are discussed in relation to various mechanisms, proposed in the literature, by which the coordination of ion uptake and transport may be maintained within the plant. We suggest that under our conditions any putative allosteric control of uptake and transport by root cortical cells was masked by an alternative mechanism, in which ion influx appears to be regulated by ion efflux to the xylem, perhaps controlled by the concentration of particular ions recycled in the phloem to the root from the shoot.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00411137
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  • 9
    Electronic Resource
    Electronic Resource
    Larger adenylate energy charge and ATP/ADP ratios in aerenchymatous roots of Zea mays in anaerobic media as a consequence of improved internal oxygen transport (1985)
    Springer
    Planta 165 (1985), S. 51-58 
    Details
    ISSN: 1432-2048
    Keywords: Adenine nucleotide ; Adenylate energy charge ; Acrenchyma ; Anaerobiosis ; Anoxia ; Gas space (root) ; Oxygen ; Root (O2 supply) ; Zea (root, oxygen)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Internal transport of O2 from the aerial tissues along the adventitious roots of intact maize plants was estimated by measuring the concentrations of adenine nucleotides in various zones along the root under an oxygen-free atmosphere. Young maize plants were grown in nutrient solution under conditions that either stimulated or prevented the formation of a lysigenous aerenchyma, and the roots (up to 210 mm long) were then exposed to an anaerobic (oxygen-free) nutrient solution. Aerenchymatous roots showed higher values than non-aerenchymatous ones for ATP content, adenylate energy charge and ATP/ADP ratios. We conclude that the lysigenous cortical gas spaces help maintain a high respiration rate in the tissues along the root, and in the apical zone, by improving internal transport of oxygen over distances of at least 210 mm. This contrasted sharply with the low energy status (poor O2 transport) in non-aerenchymatous roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392211
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  • 10
    Electronic Resource
    Electronic Resource
    Ethylene-promoted adventitious rooting and development of cortical air spaces (aerenchyma) in roots may be adaptive responses to flooding in Zea mays L (1979)
    Springer
    Planta 147 (1979), S. 83-88 
    Details
    ISSN: 1432-2048
    Keywords: Adventitious roots ; Air spaces (aerenchyma) ; Ethylene ; Oxygen ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The roots and stem base of intact, 10 day old maize (Zea mays L. cv. LG11) plants, grown in nutrient solution, were continuously aerated either with ethylene (5 μl l-1) in air or with air alone. Ethylene treatment hastened the emergence of adventitious (nodal) roots from the base of the shoot, but slowed their subsequent extension. Ethylene also promoted the collapse of cells in the cortex of these roots, with lysigenous development of prominent air spaces (aerenchyma). Non-aeration of the nutrient solution caused endogenously produced ethylene to accumulate in the roots, and stimulated both the emergence of adventitious roots and the formation of cortical air spaces in them. With non-aeration the concentration of oxygen did not fall below 1% in the equilibrium gas phase (air=20.8%). Complete deoxygenation of the nutrient solution, produced by passing oxygen-free nitrogen gas, prevented both air space formation and the evolution of ethylene by root segments. These results suggest that adventitious rooting and cortical air space formation in nodal roots in Zea mays may be stimulated by enhanced concentrations of endogenous ethylene arising either from entrapment of the gas by unstirred water layers around the roots and/or by increased biosynthesis. These responses are considered conducive to survival in waterlogged soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384595
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